1. Field of the Invention
The present invention relates to a method of controlling power, and more particularly, to a method of controlling uplink output power in a wireless communication system.
2. Discussion of the Related Art
Global System for Mobile Communication (GSM) was developed to bring together different communication systems in Europe. Further, General Packet Radio Service (GPRS) introduced packet switched data into GSM systems. The GPRS provides packet data service which means that multiple users can share the same transmission channel, only transmitting when there is data to send. GSM can be referred to as circuit-switched data service which establishes a radio resource (RR) connection and reserves the full bandwidth of that circuit-switched data during the lifetime of the RR connection. The difference with packet data service is that the packet data service can have total available bandwidth dynamically dedicated to those users who are actually sending at any given moment, providing higher utilization where users only send or receive data intermittently.
Enhanced Data Rate for GSM Evolution (EDGE) introduced 8-phase shift keying (8-PSK) into GSM/GPRS networks. EDGE can use 8-PSK as well as Gaussian Minimum Shift Keying (GMSK) of GSM as the modulation scheme. With an exception of modulation scheme of GPRS, most of non-modulation techniques of GPRS can be applied to EDGE.
Further, EDGE includes two enhanced data rates, and they are an enhanced circuit switched data service (ECSD) and an enhanced packet switched data service which is also referred to as enhanced GPRS (EGPRS). Because implementation of ECSD is regarded as impractical in the real world, EDGE can be regarded as EGPRS.
EDGE is a superset to GPRS and can function on any network with GPRS deployed on it, provided that the operator of GSM/GPRS networks implements the necessary upgrades. Further, EDGE uses different modulation and/or coding schemes such as MCS1 to MCS9 from CS1 to CS4 used for GSM/GPRS networks so as to optimize the transmission rate.
GSM/GPRS/EDGE is based on a time division multiple access (TDMA) as an access technology. In the system, a communication between a base station subsystem (BSS) and a mobile station (MS) takes place in form of time slots. Here, transmission from the BSS to the MS is referred to as downlink transmission, and the transmission from the MS to the BSS is referred to as uplink transmission GPRS is different from the older circuit-switched data (CSD) connection included in GSM standards. In CSD, a data connection establishes a circuit, and reserves the full bandwidth of that circuit during the lifetime of the connection. GPRS is packet-switched which means that multiple users share the same transmission channel, only transmitting when they have data to send. This means that the total available bandwidth can be immediately dedicated to those users who are actually sending at any given moment, providing higher utilization where users only send or receive data intermittently. Web browsing, receiving e-mails as they arrive and instant messaging are examples of uses that require intermittent data transfers, which benefit from sharing the available bandwidth.
With mobility of mobile devices using the GPRS system, it is important that services are provided effectively and efficiently between the network and the mobile device.